Federal Aviation Administration, DOT

Section 33.27

(2) The specified ultimate loads without failure, but may exhibit permanent
deformation.
[Amdt. 33-10, 49 FR 6851, Feb. 23, 1984]

Section 33.25

Accessory attachments.

The engine must operate properly
with the accessory drive and mounting
attachments loaded. Each engine accessory drive and mounting attachment must include provisions for sealing to prevent contamination of, or unacceptable leakage from, the engine interior. A drive and mounting attachment requiring lubrication for external
drive splines, or coupling by engine oil,
must include provisions for sealing to
prevent unacceptable loss of oil and to
prevent contamination from sources
outside the chamber enclosing the
drive connection. The design of the engine must allow for the examination,
adjustment, or removal of each accessory required for engine operation.
[Amdt. 33-10, 49 FR 6851, Feb. 23, 1984]

spaschal on DSK3GDR082PROD with CFR

Section 33.27 Turbine, compressor, fan, and
turbosupercharger rotor overspeed.
(a) For each fan, compressor, turbine,
and turbosupercharger rotor, the applicant must establish by test, analysis,
or a combination of both, that each
rotor will not burst when operated in
the engine for 5 minutes at whichever
of the conditions defined in paragraph
(b) of this section is the most critical
with respect to the integrity of such a
rotor.
(1) Test rotors used to demonstrate
compliance with this section that do
not have the most adverse combination
of material properties and dimensional
tolerances must be tested at conditions
which have been adjusted to ensure the
minimum specification rotor possesses
the required overspeed capability. This
can be accomplished by increasing test
speed, temperature, and/or loads.
(2) When an engine test is being used
to demonstrate compliance with the
overspeed conditions listed in paragraph (b)(3) or (b)(4) of this section and
the failure of a component or system is
sudden and transient, it may not be
possible to operate the engine for 5
minutes after the failure. Under these
circumstances, the actual overspeed

duration is acceptable if the required
maximum overspeed is achieved.
(b) When determining the maximum
overspeed condition applicable to each
rotor in order to comply with paragraphs (a) and (c) of this section, the
applicant must evaluate the following
rotor speeds taking into consideration
the part-s operating temperatures and
temperature gradients throughout the
engine-s operating envelope:
(1) 120 percent of the maximum permissible rotor speed associated with
any of the engine ratings except oneengine-inoperative (OEI) ratings of less
than 21-2 minutes.
(2) 115 percent of the maximum permissible rotor speed associated with
any OEI ratings of less than 21-2 minutes.
(3) 105 percent of the highest rotor
speed that would result from either:
(i) The failure of the component or
system which, in a representative installation of the engine, is the most
critical with respect to overspeed when
operating at any rating condition except OEI ratings of less than 21-2 minutes, or
(ii) The failure of any component or
system in a representative installation
of the engine, in combination with any
other failure of a component or system
that would not normally be detected
during a routine pre-flight check or
during normal flight operation, that is
the most critical with respect to overspeed, except as provided by paragraph
(c) of this section, when operating at
any rating condition except OEI ratings of less than 21-2 minutes.
(4) 100 percent of the highest rotor
speed that would result from the failure of the component or system which,
in a representative installation of the
engine, is the most critical with respect to overspeed when operating at
any OEI rating of less than 21-2 minutes.
(c) The highest overspeed that results
from a complete loss of load on a turbine rotor, except as provided by paragraph (f) of this section, must be included in the overspeed conditions considered
by
paragraphs
(b)(3)(i),
(b)(3)(ii), and (b)(4) of this section, regardless of whether that overspeed results from a failure within the engine

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